#include <string>

class B1{
	public:
		virtual void pvf()=0;
		virtual void vf();
		void f();
};

class D1:public B1{
	public:
		void vf();
		void f();
};

class D2:public D1{
	public:
		void pvf();
};

class B2{
	public:
		 virtual void pvf() const = 0;
}; 

class D21:public B2{
    public:
        D21(const std::string& ns);
        void pvf() const;
    private:
        std::string str;
};


class D22:public B2{
    public:
        D22(int ns);
        void pvf() const;
    private:
        int num;
};

        
